At a glance
- The five types of cardiomyopathy are hypertrophic, dilated, restrictive, arrhythmogenic, and unclassified.
- Dilated cardiomyopathy presents with dyspnea, orthopnea, paroxysmal nocturnal dyspnea, ankle edema, and weight gain.
- Takotsubo cardiomyopathy is usually precipitated by episodes of physical or emotional stress.
- The objectives of treatment in hypertrophic cardiomyopathy are to alleviate symptoms and prevent complications.
Cardiomyopathy is defined as “a myocardial disorder in which heart muscle is structurally and functionally abnormal without coronary artery disease, hypertension, valvular or congenital heart diseases.”1 Cardiomyopathy is a significant cause of sudden death in the young. Therefore, primary-care providers (PCPs) play an important role both in aiding early diagnosis as well as raising awareness of these conditions in the community.
Types of cardiomyopathy
There are five types of cardiomyopathy: hypertrophic, dilated, restrictive, arrhythmogenic, and unclassified.
Hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy (HCM) is an inherited condition. HCM is characterized by disorganized cardiac myocytes and unexplained left ventricular (LV) hypertrophy attributable to mutations in the genes encoding such sarcomeric proteins as cardiac beta-myosin heavy chain gene, troponin, and alpha-tropomyosin.
The prevalence of HCM is about 1 in 5002 and it is more common in men and blacks. The obstructive form of the disease (HOCM) is seen in 25% of cases.
Dilated cardiomyopathy. Dilated cardiomyopathy (DCM) is characterized by an LV ejection fraction <45% (normally 55%-70%) with increased (dilated) LV dimension. The condition is hereditary in 30%-40% of cases (usually autosomal dominant); however, it can be caused by acute viral (usually entero-/adenoviruses) myocarditis leading to chronic inflammation, ventricular remodeling, or dysfunction.
Restrictive cardiomyopathy. Restrictive cardiomyopathy (RCM) is subclassified into primary (Loeffler’s endocarditis, endomyocardial fibrosis) and secondary (infiltrative causes: amyloidosis, sarcoidosis; storage disorders: hemochromatosis, glycogen storage disorder, Fabry’s disease; post-radiation).
Loeffler’s endocarditis is caused by acute eosinophilic myocarditis with mural thrombosis and fibrotic thickening at the apex of one or both ventricles. Endomyocardial fibrosis is the chronic form.
Arrhythmogenic right-ventricular cardiomyopathy. Arrhythmogenic right ventricular cardiomyopathy (ARVC) is caused by fibro-fatty replacement of right ventricular (RV) myocytes due to apoptosis, inflammation (definite causes for either mechanism are as yet unknown), or genetics (familial in 30%-50% of cases, usually with autosomal dominant inheritance). Though ARVC is uncommon (1 in 5,000), it has regional clustering in northern Italy and Greece.1,3
Unclassified cardiomyopathy. This category includes left ventricular noncompaction (LVNC) and takotsubo cardiomyopathy.
LVNC results from embryogenic arrest of normal myocardial maturation, causing a loose meshwork of noncompacted myocardial fibers with deep recesses communicating with the LV cavity. Takotsubo cardiomyopathy predominantly affects women and is caused by catecholamine surges from physical or emotional stress, leading to coronary vasospasm and severe apical, mid-LV dysfunction.
It is important that cardiac symptoms in young patients are not underestimated, as this can lead to fatal delays in diagnosis.
HCM. Patients with HCM may present with dyspnea caused by diastolic dysfunction, chest pain and impaired diastole of hypertrophied myocardium, palpitations (ectopic beats, atrial fibrillation [AF] or flutter, supraventricular tachycardia or ventricular tachycardia [VT]), or presyncope/syncope due to inadequate cardiac output.
Characteristic signs of HCM include double carotid impulse, prominent “a” wave on the jugular venous pulse (JVP), laterally displaced double apical impulse, and fourth heart sound.
The ejection systolic murmur is best heard between the apex and left sternal edge radiating to the suprasternal notch, intensifying with reduced preload (standing/Valsalva maneuver) or afterload (vasodilators) and diminishing with increased preload (squatting) or afterload (handgrip).